> >> I have two tables, seemigly very similar setup; the primary key is the > >> combination of two columns. With mysqldump, however, the table > >> definition of the two tables looks different. > >> > >> Mysqldump on table 1 says > >> ... > >> UNIQUE KEY HONstid (HONstid,HONname) > >> whereas on table 2 it says > >> ... > >> PRIMARY KEY (IMstid,IMfnum) > >> > >> What is the difference? Is there any? > > > >A table can have only 1 primary key, but multiple unique constraints. > > And columns in primary keys must be NOT NULL. Columns in unique > keys can be NULL (if they are NOT NULL, then the unique key is > functionally the same as a primary key).
Ah yes Paul, thanks for adding that. With regards, Martijn Tonies Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL Server Upscene Productions http://www.upscene.com -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
